It is intended to continue study of aspects of the semi-synthetic organic chemistry of cytochalasin A and cytochalasin D. These derivatives are to be used for affinity chromatographic separation of macromolecular cytochalasin acceptors, and for their affinity-labeling. Consequences, at the molecular level, of drug binding to membranes derived from blood platelets and from selected eukaryotic microorganisms will be explored. The molecular basis for inhibition of growth and related phenomena among eubacterial species by certain cytochalasins will be investigated. The effects of cytochalasin derivatives on contractile proteins and their functional elements in vitro, will be examined both by biochemical and physical-chemical means.